AZO compound photoreceptor having napthol substiuents

ABSTRACT

An azo compound with the following general formula (I): ##STR1## wherein X is selected from the group consisting of hydrogen atom, lower alkyl group, lower alkoxy group, halogen atom and cyano group; 
     Y is phenylene or naphthylene group; 
     Z 1  and Z 2  are independently the divalent group represented by the following formula: ##STR2##  wherein A is a divalent group derived from the aromatic hydrocarbon or heterocyclic compound including one or more nitrogen atoms in the ring; and 
     n is 1 or 2, 
     is disclosed. Such compounds are useful in forming a photosensitive layer of an electrophotographic photoreceptor.

This is a divisional of copending application Ser. No. 686,991 filed onDec. 27, 1984 now U.S. Pat. No. 4,618,555 issued Oct. 21, 1986.

This invention relates to a novel azo compound suitable as aphotoconductive substance in a photosensitive layer of anelectrophotographic photoreceptor which has excellent sensitivity andexcellent durability, and an electrophotographic photoreceptor, thephotosensitive layer of which contains the photoconductive substance ofthe novel azo compound.

Hitherto inorganic photoconductive substances such as selenium, cadmiumsulfide, zinc oxide and the like have been known to be contained in thephotosensitive layer of an electrophotographic photoreceptor. And as asubstitute of such inorganic photoconductive substance, organicphotoconductive substances such as polyvinyl carbazole have beenrecently proposed and some of them are commercialized owing to theiradvantages over the inorganic photoconductive substances which aredescribed as follows:

(1) they are light in weight;

(2) they can be easily formed to be a film;

(3) they can be easily formed to be the photoreceptor; and

(4) by selection a transparent photoreceptor can be formed.

Although the organic photoconductive substances have the advantagesmentioned above, they are neither preferably nor frequently available inan electrophotographic photoreceptor because the elctrophotographicphotoreceptor having the photosensitive layer in which the organicphotoconductive substance is incorporated provides sensitivity anddurability inferior to inorganic photoconductive substances.

It is an object of this invention to provide an electrophotographicphotoreceptor having excellent sensitivity and excellent durability.

It is another object of this invention to provide a photoconductivesubstance which is capable of forming such an electrophotographicphotoreceptor.

Other objects of this invention will be apparent from the followingdescriptions.

In accordance with this invention, the electrophotographic photoreceptorhaving excellent sensitivity and excellent durability can be provided byusing a specified azo compound as the organic photoconductive substance.

The azo compound used in this invention as the organic photoconductivesubstance (hereinafter referred to as "the present compound") has thefollowing general formula (I): ##STR3## wherein X is selected from thegroup consisting of hydrogen atom, lower alkyl group, lower alkoxygroup, halogen atom and cyano group;

Y is phenylene or naphthylene group;

Z₁ and Z₂ are independently the divalent group represented by thefollowing formula: ##STR4## wherein A is a divalent group derived fromthe aromatic hydrocarbon or heterocyclic compound including one or morenitrogen atoms in the ring; and

n is 1 or 2.

As the aromatic hydrocarbon from which the divalent group A is derived,both monocyclic and condensed polycyclic hydrocarbon may be used and asthe heterocyclic compounds, the compounds having five- to ten-memberedring in which one or more nitrogen atoms, preferably one or two nitrogenatoms are included may be used. Typically, o-phenylene, o-naphthylene,peri-naphthylene, 1,2-anthraquinonylene, 9,10-phenanthrylene,pyrazole-3,4-diyl, pyridine-2,3-diyl, pyrimidine-4,5-diyl,indazole-6,7-diyl, benzimidazole-5,6-diyl and quinoline-6,7-diyl areexemplified as such a divalent group.

The present compound having the general formula (I) wherein X ishydrogen atom, Y is phenylene group, Z₁ and Z₂ are independently thedivalent group represented by the following formula: ##STR5## wherein Ais o-phenylene, o-naphthylene, peri-naphthylene, pyridine-2,3-diyl orpyrimidine-2,3-diyl, especially o-phenylene or o-naphthylene and n is 1or 2 is preferable.

The above-mentioned divalent group may be substituted with anysubstituent, for example, alkyl group such as methyl, ethyl, n-,i-propyl, n-, i-butyl and n-hexyl; alkoxy group such as methoxy, ethoxy,propoxy and butoxy; amino group; alkylamino group such as methylaminoand ethylamino; dialkylamino group such as dimethylamino anddiethylamino; hydroxy group; nitro group; cyano group; halogen atom suchas fluorine, chlorine, bromine and iodine; carboxyl group;alkoxycarbonyl group such as ethoxycarbonyl; carbamoyl group; aryloxygroup such as phenoxy; arylalkoxy group such as benzyloxy; andaryloxycarbonyl group such as phenyloxycarbonyl. Among theabove-mentioned substituents, alkyl, alkoxy, amino, alkylamino,dialkylamino, nitro, halogen, hydroxy and carboxyl are preferable.Methyl, methoxy, nitro, chlorine, hydroxy, amino and dimethylamino aremore preferable.

The present compound can be easily prepared according to the knowncoupling reaction. For example, the coupling ingredient represented bythe following general formula (II-a) and/or (II-b): ##STR6## wherein Ais as defined above, is reacted with a tetrazonium salt of the diaminerepresented by the following general formula (III): ##STR7## wherein X,Y and n are as defined above, to obtain the present compound.

The coupling reaction is generally carried out in water and/or anorganic solvent such as dimethylsulfoxide, N,N-dimethylformamide,N-methylpyrrolidone and the like at a temperature of not more than 30°C. for about 1 to 10 hours.

The coupling ingredient having the general formula (II-a) and/or (II-b)may be obtained in the manner described in J. Chem. Soc., 1937, 1764,that is, by warming 3-hydroxynaphthalic anhydride represented by theformula (IV): ##STR8## and aromatic diamine represented by the formula(V): ##STR9## wherein A is as defined above, in solvent such as aceticacid to condensate with dehydration.

According to the above condensation reaction, the coupling ingredient isobtained in a form of a mixture of isomers (II-a) and (III-b), but bothisomers can be used separately or in a mixture thereof for thepreparation of the present compound.

The aromatic diamine having the general formula (V) may be o- orperi-primary diamine which is unsubstituted or substituted with one ormore of any substituent, for example nitro, alkyl such as methyl, ethyland propyl, alkoxy such as methoxy, halogen such as chlorine, bromineand iodine, carboxyl, alkoxycarbonyl such as methoxycarbonyl. Thefollowing diamine is preferably used:

o-phenylenediamines such as o-phenylenediamine,4-nitro-o-phenylenediamine, 3,5-dinitro-o-phenylenediamine,4-methyl-o-phenylenediamine, 4-ethyl-o-phenylenediamine,4-i-propyl-o-phenylenediamine, 4,5-dimethyl-o-phenylenediamine,4-methoxy-o-phenylenediamine, 4,5-diethoxy-o-phenylenediamine,4-chloro-o-phenylenediamine, 4-bromo-o-phenylenediamine,4-iodo-o-phenylenediamine, 4-carboxy-o-phenylenediamine and4-methoxycarbonyl-o-phenylenediamine;

diamine of condensed polycyclic aromatic hydrocarbon such as1,2-naphthylenediamine, 2,3-naphthylenediamine, 1,8-naphthylenediamine,1,2-diaminoanthraquinone and 9,10-diaminophenanthrene;

diamine of hetero-monocyclic compound such as 2,3-diaminopyridine,3,4-diaminopyridine, 4,5-diaminopyridine and 3,4-diaminopyrazol;

diamine of condensed heterocylic compound such as 5,6-diaminoindazole,6,7-diaminoindazole, 5,6-diaminobenzimidazole and 5,6-diaminoquinoline;and a derivative thereof.

It is possible to obtain the coupling ingredient having the generalformula (II-a) and (II-b) by other methods such as a method similar tothe above-coupling reaction except the use of 3-hydroxynaphthalic acidor its ester instead of 3-hydroxynaphthalic anhydride; the method ofreductively condensing 3-hydroxynaphthalic anhydride withmonoaminomononitro compound (instead of aromatic diamine); the method ofcondensing the aromatic diamine with 3-sulphonaphthalic anhydridefollowed by hydrolyzing the sulfo group; and the like.

On the other hand, the diamine having the general formula (III) can bealso prepared according to any known method. For example, the diaminehaving the general formula (III) wherein n is 1, X and Y are as definedabove is synthesized in accordance with the following reaction scheme.##STR10## When the diamine having the general formula (III) wherein n is2 is required, the reaction shown above may be repeated. ##STR11##

As mentioned above, the present compound can be obtained by reacting thecoupling ingredient of the general formula (II-a) and/or (II-b) with thetetrazonium salt of the diamine of the general formula (III). If themixture of the isomers (II-a) and (II-b) is used as the couplingingredient, the present compound is obtained in a form of a mixture ofthe following isomers (I-a) to (I-c), which mixture is applicable to theformation of the electrophotographic photoreceptor according to thisinvention as it is. ##STR12##

The present compound may be incorporated in the photosensitive layer ofthe electrophotographic photoreceptor in any known form. Preferably, thepresent compound is incorporated in the layer for generating the chargecarriers (hereinafter referred to as "the generating layer") which iscombined with the layer for transporting the charge carriers(hereinafter referred to as "the transporting layer") to form alaminated-typed photosensitive layer since the present compound has theadvantage of being suitable as the material for generating the chargecarriers in a photoreceptor, that is, the advantage to be able togenerate the charge carriers with high efficiency when light isabsorbed.

The generating layer in which the present compound is incorporated isformed by any suitable method. For example, the coating solution inwhich the present compound is dissolved or dispersed in a suitablesolvent with or without a binder polymer is coated on a conductive basefollowed by drying to form the generating layer.

The solvent used for dissolving or dispersing the present compound toprepare the coating solution is preferably selected from the followingsolvents:

amine such as butylamine and ethylenediamine;

ether such as tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane anddiethyleneglycol dimethyl ether;

ketone such as methyl ethyl ketone and cyclohexanone;

aromatic hydrocarbon such as toluene and xylene;

alcohol such as methanol, ethanol and isopropanol;

ester such as ethyl acetate, methyl formate and methylcellosolveacetate;

chlorinated aliphatic or aromatic hydrocarbon such as dichloroethane andchloroform; and

others such as N,N-dimethylformamide, acetonitrile, N-methylpyrrolidoneand dimethyl sulfoxide.

The above-mentioned solvent may be mixed. And when the binder polymer isused together for the formation of the generating layer, it ispreferable to select a solvent which has the ability of dissolving thebinder polymer.

As the binder polymer, the homopolymer or copolymer of vinyl compoundsuch as styrene, vinyl acetate, acrylic acid ester and methacrylic acidester, polyester, polycarbonate, polysulfone, polyvinylbutyral, theresin of phenoxy, urethane and epoxy, and cellulose ester or ether areexemplified. The amount used of the binder polymer is generally 0.1 to 5parts by weight based on 1 part by weight of the present compound. Andpreferably, the present compound is present in the binder polymer in astate of finely divided particles of not more than 1 micron in diameter.

The generating layer has the thickness of generally not more than a fewmicrons, preferably not more than 1 micron.

As the conductive base on which the generating layer is provided, anyknown conductive base for an electrophotographic photoreceptor isavailable. Generally, a metal such as aluminum or copper in a form ofdrum, sheet and the like, or the laminate or deposit of such a metal isused. Alternatively, a film, sheet, drum or pipe made of plastic orpaper on which a conductive material such as metal powder, carbon black,carbon fiber, cupric iodate, polymeric electrolyte in a suitable binderis coated, or in which the above-mentioned conductive material is mixedso as to make conductive may also be used.

The transporting layer is usually and preferably laminated on thegenerating layer since the former prevents the latter from wearing andbecoming dirty due to the thin thickness of the latter. Of course, theconstruction of laminating the generating layer on the transportinglayer is possible.

The transporting layer acts to transport the charge carriers generatedin the generating layer and so this layer contains necessarily a mediumfor transporting the charge carriers. As the medium for transporting thecharge carriers, a medium for transporting the electrons and/or a mediumfor transporting the holes is used. The medium for transporting theelectrons may comprise an electron-attracting compound having theelectron-attracting group such as nitro, cyano and ester group, forexample 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone or2,4,5,7-tetracyanoquinodimethane. While, the medium for transporting theholes may comprise the electron-donating compound, for example theheterocyclic compound such as carbazole, indole, imidazole, oxazole,thiazole, oxadiazole, pyrazole, pyrazoline and thiadiazole, anilinederivative, hydrazine derivative, hydrazone derivative or a polymerhaving a group derived from the above-mentioned compound in theprincipal or side chain such as polyvinylcarbazole and polyglycidylcarbazole. Among them, the use of the hydrazone represented by thegeneral formula (XVII) or (XVIII) shown later or a mixture thereof ispreferable. ##STR13## wherein R¹ is alkyl or aralkyl which may besubstituted, R² is alkyl which may be substituted, allyl, phenyl,naphthyl or aralkyl, and Z³ is hydrogen, halogen, alkyl or alkoxy;##STR14## wherein X¹, Y¹ and Z⁴ are independently hydrogen, lower alkylor alkoxy, phenoxy or arylalkoxy, R³ is hydrogen, lower alkyl, allyl,phenyl or aralkyl, m and l is 1 or 2, and p is 0 or 1.

The transporting layer is formed in a similar method to the method forforming the generating layer. When the medium for transporting thecharge carriers comprises a low-molecular compound, it is preferable todissolve the compound in the binder polymer. The compound as the mediumfor transporting the charge carriers is used in an amount of 0.2 to 1.5part by weight, preferably 0.3 to 1.2 part by weight based on 1 part byweight of the binder polymer.

The transporting layer has the thickness of generally 5 to 50 microns,preferably 10 to 30 microns.

The photosensitive layer thus obtained may contain any known sensitizer.The sensitizer is suitably a material which is able to form a complexfor transporting the charge with the organic photoconductive compound,of which illustrative examples are Lewis acid and dye. The Lewis acidmay be the electron-attractive compound, for example quinone such aschloranil, 2,3-dichloro-1,4-naphthoquinone, 2-methyl-anthraquinone,1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone,2-chloroanthraquinone and phenanthrene quinone, aldehyde such as4-nitrobenzaldehyde, ketone such as 9-benzoylanthracene, indandione,3,5-dinitrobenzophenone and 3,3',5,5'-tetranitrobenzophenone, acidanhydride such as phthalic anhydride and 4-chloronaphthalic anhydride,cyano compound such as tetracyanoethylene, terephthalalmalononitrile,4-nitrobenzalmalononitrile and 4-(p-nitrobenzoyloxy)benzalmalononitrile, phthalide such as 3-benzalphthalide,3(α-cyano-p-nitrobenzal)phthalide and3-(α-cyano-p-nitrobenzal)-4,5,6,7-tetrachlorophthalide are exemplified.As the dye, triphenyl methane dye such as methyl violet, brilliant greenand crystal violet, thiazine dye such as methylene blue, quinone dyesuch as quinizarin, cyanin dye and pyrylium salt such as thiapyryliumsalt and benzopyrylium salt are exemplified.

In addition to the sensitizer, the photosensitive layer may contain anyknown plasticizer such as phthalic acid ester, phosphoric acid ester,epoxy compound, chlorinated paraffin, chlorinated fatty acid ester andmethyl naphthalate, whereby the film-formability, the flexibility aswell as the mechanical strength of the layer is improved.

If necessary, the adhesive layer, the intermediate layer and/or thetransparent insulating layer are provided in the photoreceptor.

The photoreceptor having the photosensitive layer in which the presentcompound is incorporated has the following advantages:

photographic sensitivity is high;

color sensitivity is high;

photographic sensitivity and chargeability are almost

unchanged even with repeated use;

fatigue against light is little; and

durability is very good.

Owing to the above-mentioned advantages, the photoreceptor according tothis invention is widely applied in the electrophotography, for examplein the electrophotographic copying machine. In the photoreceptor of thisinvention the maximum wavelength to which it can be sensitive is 600 to650 nm. Therefore, the photoreceptor of this invention is applicable inthe printer employing laser, OFT(optical fiber tube) and LED(light-emitting diode).

This invention will be more specifically described with the aid of thefollowing specific, but non-limiting examples.

EXAMPLE 1 Synthesis of Compound (Compound No. 1)

(a) 13.8 parts by weight of 3-hydroxynaphthalic anhydride (manufac. byTOKYO KOGYO CO., Ltd.) and 9.2 parts by weight of o-phenylenediamine(manufac. by TOKYO KASEI KOGYO CO., Ltd.) were dissolved in a mixedsolvent of 30 parts by weight of acetic acid and 150 parts by weight ofnitrobenzene while stirring and reacted at the boiling point of aceticacid for 2 hours. After the completion of reaction, a reaction mixturewas allowed to stand at room temperature to crystallize out followed bycollecting the crystals through filtration, washing with methanol anddrying to obtain 17.8 parts by weight of a crystalline product yellow incolor and feather in form.

The characteristics of the thus obtained product were as follows.

(1) melting point; more than 320° C.,

(2) elementary analysis; C₁₈ H₁₀ O₂ N₂

    ______________________________________                                                 C (%)      H (%)   N (%)                                             ______________________________________                                        theoretical:                                                                             75.54        3.53    9.78                                          experimental:                                                                            75.50        3.49    9.72                                          ______________________________________                                    

According to the above-mentioned data and IR spectrum, it was confirmedthat the product was 2-hydroxy- and5-hydroxy-7H-benzimidazo-[2,1-a]benz[de]isoquinoline-7-on.

(b) Firstly 1.2 part by weight of 4,4-diaminoazobenzene was dissolved in30 parts by weight of glacial acetic acid and then 7 parts by weight ofan aqueous 35% hydrochloric acid solution was added dropwise thereintowhile stirring. While 30 minutes, 30 parts by weight of water wasfurther added and then cooled to the temperature of 0° to 50° C. Thethus cooled mixture was added dropwise into a solution of 1.6 parts byweight of sodium nitrite in 5 parts by weight of water while stirring.

After 30 minutes, 15 parts by weight of an aqueous 42% tetrafluoroboricacid solution was added dropwise and crystallized out a correspondingtetrazonium tetrafluoroborate, which was then collected throughfiltration.

(c) The tetrazonium salt obtained in above (b) without drying dissolvedin 600 parts by weight of dimethylsulfoxide at room temperature wasadded dropwise into a solution in which 3.2 parts by weight ofisoquinoline-7-on obtained in above (a) was dissolved in 460 parts byweight of dimethylsulfoxide while heating and then cooled to roomtemperature, and then reacted using a solution of 5 parts by weight ofsodium acetate in 1.2 parts by weight of water while maintaining areaction temperature at about 20° C. followed by purifying according toconventional method to obtain 3.3 parts by weight of the solid producthaving dark purple in color.

The characteristics of the thus obtained product were as follows.

(1) melting point; more than 320° C.,

(2) elementary analysis; C₄₈ H₂₆ N₁₀ O₄

    ______________________________________                                                 C (%)      H (%)   N (%)                                             ______________________________________                                        theoretical:                                                                             71.46        3.23    17.37                                         experimental:                                                                            71.19        3.04    17.28                                         ______________________________________                                    

(3) IR spectrum; as shown in FIG. 1 of the accompanying drawings.

According to the above-mentioned data, it was confirmed that the productwas a mixture of trisazo compound having the following formula.##STR15##

EXAMPLE 2 Synthesis of Compound (Compound No. 2)

(a) 12.8 parts by weight of 3-hydroxynaphthalic anhydride (maufac. byTOKYO KASEI KOGYO CO., Ltd.) and 7.3 parts by weight of3,4-diaminotoluene (manufac. by TOKYO KASEI KOGYO CO., Ltd.) weredissolved in a mixed solvent of 30 parts by weight of acetic acid and150 parts by weight of nitrobenzene while stirring and reacted at theboiling temperature of acetic acid for 2 hours. After the completion ofthe reaction, a reaction mixture was allowed to stand at roomtemperature to crystallize out followed by collecting throughfiltration, washing with methanol and drying to obtain 17.8 parts byweight of the crystalline product yellow in color and feather in form.

The characteristics of the thus obtained product were as follows.

(1) melting point; not more than 320° C.,

(2) elementary analysis; C₁₉ H₁₂ O₂ N₂

    ______________________________________                                                 C (%)      H (%)   N (%)                                             ______________________________________                                        theoretical:                                                                             76.00        4.00    9.33                                          experimental:                                                                            75.83        3.89    9.31                                          ______________________________________                                    

According to the above-mentioned data and IR spectrum, it was confirmedthat the product was 2-hydroxy- and5-hydroxy-7H-3',[4']methylbenzimidazo[2,1-a]benz[de]isoquinoline-7-on.

(b) In a similar manner to that of Example 1 except that one of thecoupling ingredients was replaced by isoquinoline-7-on prepared in above(a), solid product dark purple in color was obtained.

The characteristics of the thus obtained product were as follows.

(1) melting point; more than 320° C.,

(2) elementary analysis; C₅₀ H₃₀ N₁₀ O₄

    ______________________________________                                                 C (%)      H (%)   N (%)                                             ______________________________________                                        theoretical:                                                                             71.94        3.60    16.79                                         experimental:                                                                            71.83        3.18    16.53                                         ______________________________________                                    

(3) IR spectrum; as shown in FIG. 2 of the accompanying drawings.

According to the above-mentioned data, it was confirmed that the productwas a mixture of trisazo compound having the following formula.##STR16##

EXAMPLE 3 Synthesis of Compound (Compound No. 3)

The tetrazonium salt was prepared in the same manner as that of Example1 except that 4,4'-diaminoazobenzene was replaced by(4-aminophenyl)azo-4'-aminonaphthalene. This tetrazonium salt wassubjected to the coupling reaction with isoquinoline-7-on prepared inExample 2(a) described above to obtain the solid product having darkpurple in color.

The characteristics of thus obtained product were as follows.

(1) melting point; more than 320° C.,

(2) elementary analysis; C₅₄ H₃₂ N₁₀ O₄

    ______________________________________                                                 C (%)      H (%)   N (%)                                             ______________________________________                                        theoretical:                                                                             73.30        3.62    15.84                                         experimental:                                                                            72.91        3.32    15.38                                         ______________________________________                                    

(3) IR spectrum; as shown in FIG. 3 of the accompanying drawings.

According to the above-mentioned data, it was confirmed that the productwas a mixture of trisazo compound having the following formula.##STR17##

In the similar manner, the compounds of Compound No. 4 to 21 weresynthesized.

EXAMPLE 4 Formation of photoreceptor

Into 0.45 part by weight of each of the present compounds synthesized inthe above-mentioned Examples which were dispersed in 30 parts by weightof cyclohexanone by means of a sand grinder, 0.9 part by weight ofpolyester (Vyrone 200® manufact. by TOYOBO CO., LTD.) was added anddissolved to prepare a dispersion.

The thus prepared dispersion was coated on an aluminum layer depositedon a polyester film of 100 microns in thickness so as to provide driedfilm of 0.6 g/m² thickness and dried to form a generating layer.

Onto this layer, a solution of 80 parts by weight ofN-ethylcarbazole-3-aldehyde-diphenylhydrazone and 100 parts by weight ofmethacrylic resin (Dianal® manufac. by Mitsubishi Rayon Co., Ltd.) in550 parts by weight of toluene to provide dried film of 10 micronsthickness and dried to form a transporting layer. In this way, atwo-layered photosensitive layer comprising the transporting layer onthe generating layer was provided on the aluminum base to form aphotoreceptor.

The sensitivity of the photoreceptor was investigated on the basis ofhalf-exposure (E_(1/2)) determined as follows.

The photoreceptor was submitted to a corona discharge of -6.5 KV in darkso as to charge the surface of the photoreceptor, and the suface voltage(initial surface voltage) was measured by means of a test device forelectrostatic copying paper (Model SP-248 manufac. by Kawaguchi ElectricWorks, Ltd.). Then the surface of the photoreceptor was irradiated bywhite light of 5 lux till the surface voltage was reduced by half of theinitial surface voltage. The half-exposure (E_(1/2)) was calculated fromthe time required for reducing by half.

The results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________     ##STR18##                                                                    Compound No.                                                                          X   Y       Z                n E.sub.1/2  (lux ·             __________________________________________________________________________                                           sec)                                   1       H                                                                                  ##STR19##                                                                             ##STR20##       1 3.2                                    2       H                                                                                  ##STR21##                                                                             ##STR22##       1 3.1                                    3       H                                                                                  ##STR23##                                                                             ##STR24##       1 3.4                                    4       H                                                                                  ##STR25##                                                                             ##STR26##       1 2.0                                    5       H                                                                                  ##STR27##                                                                             ##STR28##       1 4.9                                    6       H                                                                                  ##STR29##                                                                             ##STR30##       1 5.3                                    7       H                                                                                  ##STR31##                                                                             ##STR32##       1 7.2                                    8       H                                                                                  ##STR33##                                                                             ##STR34##       1 4.6                                    9       CN                                                                                 ##STR35##                                                                             ##STR36##       1 3.6                                    10      CH.sub.3                                                                           ##STR37##                                                                             ##STR38##       1 8.2                                    11      H                                                                                  ##STR39##                                                                             ##STR40##       1 18.3                                   12      OCH.sub.3                                                                          ##STR41##                                                                             ##STR42##       1 9.2                                    13      H                                                                                  ##STR43##                                                                             ##STR44##       1 11.3                                   14      Cl                                                                                 ##STR45##                                                                             ##STR46##       1 8.7                                    15      H                                                                                  ##STR47##                                                                             ##STR48##       1 13.2                                   16      H                                                                                  ##STR49##                                                                             ##STR50##       2 6.2                                    17      CN                                                                                 ##STR51##                                                                             ##STR52##       1 3.8                                    18      H                                                                                  ##STR53##                                                                             ##STR54##       2 2.8                                    19      H                                                                                  ##STR55##                                                                             ##STR56##       2 1.2                                    20      H                                                                                  ##STR57##                                                                             ##STR58##       2 1.9                                    21      H                                                                                  ##STR59##                                                                             ##STR60##       2 2.8                                    __________________________________________________________________________

What is claimed is:
 1. An azo compound having the formula: ##STR61##wherein X is selected from the group consisting of hydrogen, loweralkyl, lower alkoxy, halogen and cyano;Y is phenylene or naphthylene; Z₁and Z₂ are independently the divalent group represented by the followingformula: ##STR62## where A is derived form an aromatic hydrocarbon orheterocyclic compound including one or more nitrogen atoms in the ring;and n is 1 or
 2. 2. The compound of claim 1, wherein the aromaticcompound from which the divalent group is derived is a monocyclic orcondensed polycyclic aromatic hydrocarbon.
 3. The compound of claim 2,wherein the divalent group derived from the aromatic hydrocarbon iso-phenylene, o-naphthylene, peri-naphthylene, 1,2-anthraquinonylene,9,10-phenanthrylene.
 4. The compound of claim 3, wherein the divalentgroup derived from the aromatic hydrocarbon is o-phenylene,o-naphthylene or peri-naphthylene.
 5. The compound of claim 1, whereinthe heterocyclic compound from which the divalent group is derived isthe five- to ten-membered ring compound.
 6. The compound of claim 5,wherein the divalent group derived from the heterocyclic compound ispyrazole-3,4-diyl, pyridine-2,3-diyl, pyrimidine-4,5-diyl,indazole-6,7-diyl, benzimidazole-5,6-diyl or quinoline-6,7-diyl.
 7. Thecompound of claim 6, wherein the divalent group derived from theheterocyclic compound is pyridine-2,3-diyl or pyrimidine-4,5-diyl. 8.The compound of any one of claims 2, 3, 4, 6, 7, 1 and 5, wherein thearomatic hydrocarbon or the heterocyclic compound from which thedivalent group is derived is substituted with alkyl, alkoxy, amino,alkylamino, dialkylamino, hydroxy, nitro, cyano, halogen, carboxyl,akloxycarbonyl, carbamoyl, aryloxy, arylalkoxy or aryloxycarbonyl
 9. Thecompound of claim 8 wherein the substituent is alkyl, alkoxy, amino,alkylamino, dialkylamino, nitro, halogen, hydroxy or carboxyl.
 10. Thecompound of claim 9, wherein the substituent is methyl, methoxy, nitro,chlorine hydroxy, amino or dimethylamino.
 11. The compound of any one ofclaims 1, 2, 3, 4, 5, 6, 7, 9, and 10, wherein X is hydrogen, Y isphenylene, Z₁ and Z₂ are independently the divalent group represented bythe following formula: ##STR63## "substituted or unsubstitutedo-phenylene or substituted or unsubstituted o-naphthylene"with--o-phenylene or o-naphthylene which is unsubstituted or substitutedwith alkyl, alkoxy, amino, alkylamino, dialkylamino, nitro, halogen,hydroxy or carboxyl.
 12. The compound of claim 8 wherein X is hydrogen ,Y is phenylene, Z₁ and Z₂ are independently the divalent grouprepresented by the following formula: ##STR64## wherein A is o-phenyleneor o-naphthylene which is unsubstituted or substituted with alkyl,alkoxy, amino, alkylamino, dialkylamino, nitro, halogen, hydroxy orcarboxyl, and n is 1 or 2.